Method of making stressed briquettes



Dec. 13, 1966 R GRAHAM ETAL 3,291,593

METHOD OF MAKING STRESSED BRIQUETTES Filed Oct. 1, 1964 Heated Iran I /"0xl'de Fines l/VVENTOl-PS. RA Y L. GRAHAM and EUGENE A. PELCZARSK/ Ar forney United States Patent O 3,291,593 METHOD OF MAKING STRESSED BRIQUETTES Ray L. Graham, Middlesex Township, Butler County, and Eugene A. Pelczarski, West Deer Township, Allegheny County, Pa, assignors to United States Steel Corporation, a corporation of Delaware Filed Oct. 1, 1964, Ser. No. 400,824 3 Claims. (Cl. 753) This invention relates to an improved method of making iron oxide briquettes and to the resulting product.

Before iron oxide fines can be charged to a blast furnace, they must be formed into agglomerates large enough not to be blown from the furnace. The agglomerates must have suflicient mechanical strength to avoid excessive degradation in handling and also to withstand temperatures and conditions encountered in blast furnace operation. Briquetting is one of several processes currently used for agglomerating iron oxide fines. Usually a briquetting process involves pressing the fines into pillow-shaped bodies under high pressures in a roll-type press. At high temperatures the fines can be briquetted without a binder, but it is difficult to obtain the necessary strength characteristics.

An object of our invention is to provide an improved method of making iron oxide briquettes in which the briquettes are prestressed to increase their strength.

A more specific object is to provide an improved method of making iron oxide briquettes in which iron oxide fines are heated to relatively high temperatures and compacted into pillow-shaped briquettes, and a heated wire is embedded in each briquette to prestress it.

A further object is to provide as an article of manufacture an iron oxide briquette which contains a length of wire prestressing the compacted iron oxide body.

In the drawing:

The single figure is a diagrammatic side elevational view of an apparatus for performing our briquetting method.

According to our invention, we heat minus inch iron oxide fines to a temperature in the range of 1000 to 2000 F. We feed the heated fines to a conventional rolltype briquetting press 10, which includes a feed chamber 12, a screw feeder 13, and a pair of power-driven rolls 14. The rolls have a plurality of mating pillow-shaped briquette-forming cavities 15 extending in rows around their circumferences. The rolls compact the fines under a load of about 20,000 to 100,000 pounds per inch of effective roll width to form briquettes 16. We also feed a continuous length of steel wire 17 from a spool 18 or the like between the rolls, whereby the wire is embedded in the briquettes 16. Contact with the hot fines heats the wire and causes it to expand lengthwise. Optionally we can supply additional heat to the wire, as with a gas flame. The wire has a greater coefficient of thermal expansion than the iron oxide. After the briquettes cool, frictional forces lock the wire in place and prevent its contracting. Hence the wire applies a compressive stress to each briquette. Subsequently we cut the wire to separate the individual briquettes.

As an example to demonstrate the benefits our invention attains, we heated minus inch hematite ore to 1400 F and briquetted the heated ore in a roll-type press. To evaluate the strength characteristics of the briquettes, we tumbled them in a drum (36 inches diameter x inches wide) for 25, 100 and 200 revolutions. At each 3,20L593 Patented Dec. 13, 1966 of the specified number of revolutions, we screened the tumbled product to determine its size consist. The quantity of material retained on a one-half inch screen is an indication of the briquette strength. We repeated the test under the same conditions, except that we continuously fed 17 B & S gage bailing wire into the press in accordance with the present invention. The results were as follows:

These results show the prestressed briquettes are considerably stronger than the others.

From the foregoing description and example it is seen that our invention affords a simple method of strengthening iron oxide briquettes, as well as an improved product. In briquetting at elevated temperatures without a binder, it is of course desirable to operate at the lowest temperature and pressure which produce a satisfactory product. Our invention produces satisfactory briquettes at 1400 E, where heretofore temperatures of 1900 to 2000 F. have been needed.

While we have shown and described only a single embodiment of our invention, it is apparent that modifications may arise. Therefore, We do not Wish to be limited to the disclosure set forth but only by the scope of the appended claims.

We claim:

1. A method of briquetting iron oxide fines comprising heating the fines to a temperature in the range of about 1000 to 2000 F., compacting the heated fines in a roll-type briquetting press under a load of about 20,000 to 100,000 pounds per inch of effective roll width to form briquettes, and embedding a length of heated wire in each briquette, said wire having a greater coeflicient of thermal expansion than the iron oxide, whereby it prestresses each briquette on cooling.

2. A method of briquetting iron oxide fines comprising heating the fines to a temperature in the range of about 1000 to 2000 F., compacting the heated fines in a roll-type briquetting press under a load of about 20,000 to 100,000 pounds per inch of efiective roll width to form briquettes, feeding a continuous length of steel wire into the press, heating said wire by contact with the fines, embedding the heated wire in the briquettes as they are formed, said wire having a greater coefiicient of thermal expansion than the iron oxide, whereby it prestresses each briquette on cooling, and cutting said wire between briquettes.

3. A briquette of compacted iron oxide fines including a steel wire extending through the iron oxide fines, said wire having a greater coefficient of thermal expansion than the iron oxide and being in a stressed condition and frictionally held to the iron oxide to prestress the briquette.

No references cited.

BENJAMIN HENKIN, Primary Examiner. 

1. A METHOD OF BRIQUETTING IRON OXIDE FINES COMPRISING HEATING THE FINES TO A TEMPERATURE IN THE RANGE OF ABOUT 1000 TO 2000F., COMPACTING THE HEATED FINES IN A ROLL-TYPE BRIQUETTING PRESS UNDER A LOAD OF ABOUT 20,000 TO 100,000 POUNDS PER INCH OF EFFECTIVE ROLL WIDTH TO FORM BRIQUETTES, AND EMBEDDING A LENGTH OF HEATED WIRE IN EACH BRIQUETTE, SAID WIRE HAVING A GREATER COEFFICIENT OF THERMAL EXPANSION THAN THE IRON OXIDE, WHEREBY IT PRESTRESSES EACH BRIQUETTE ON COOLING. 